A common type of flexible door employs a drive mechanism for raising and lowering the door and includes an electrically powered motor which applies torque to a roller causing the door to wind up on or to unwind from the roller in positioning the door in either the open or closed position, or any position therebetween. A common type of flexible curtain is comprised of a lightweight, strong fabric material and includes an electric motor typically connected to a roller mechanism via a reduction gear to reduce the number of revolutions of the electric motor per unit distance of travel of the flexible door in raising and lowering the door. Movable structures of this type can be used either to cover an opening, such as a doorway in a building structure, or they may be used as a movable partition, wall or curtain in the structure.
When used as a partition, or curtain, this roll-up structure may span large distances in the building structure. These types of flexible curtains isolate the inside of the building structure from the elements, such as wind, rain, snow and sunlight, while permitting the building structure to be opened up so as to provide access to the outside when the environment is more hospitable.
As the applications for these types of flexible curtains have increased, additional demands have been placed on their structure and operation. For example, these types of flexible curtains are being used to span increasingly longer distances within the building structure. This, of course, places increasing demands upon the curtain support and drive, or displacement, system. Higher power ratings are required for the curtain drive mechanism, which typically includes an electrically powered motor, for increasing heights and horizontal distances spanned by the curtain. In addition, the curtain support system, which typically includes a horizontal, elongated rod, must be stronger to accommodate the increased weight of curtains spanning larger openings and must itself be lightweight to compensate for the increased weight of the curtain. This further increases the power requirements to operate the flexible curtain. In addition, the increased weight of the curtain with longer curtain lengths gives rise to the application of large torques arising from the unwinding forces exerted by the long length of the rolled-up curtain on the curtain support/drive mechanism. This increased torque places increased stress on the curtain support structure and drive mechanism. Where a roll-up rod is attached to a lower end of the flexible curtain, a complicated displacement and support mechanism is typically required to accommodate vertical movement of the rod during curtain roll-up and unrolling.
These types of curtains are increasingly being used in dairy barns wherein large numbers of cows are maintained and housed. Roll-up curtains are particularly adapted for this type of environment because they allow for easy and quick control of air flow as well as access to the outside environment. Sufficient ventilation is important in this environment to allow warm moisture to escape, to protect the cows from drafts and cold winter air, and to keep the cows dry. The increase in the size of herds has increased the demand for larger buildings offering improved ventilation and environmental isolation characteristics. This has necessitated the adoption of curtains of longer length with corresponding increased demands on the curtain support structure and drive mechanism.
The present invention addresses the aforementioned increased demands on roll-up curtains used in various applications by providing a curtain support and drive arrangement which accommodates the increased weights of longer curtain sections forming the walls of larger structures. The curtain support and drive arrangements used in the present invention are particularly designed to accommodate the large torques encountered when operating roll-up curtains of increased length.